On 27 November 2012 at 1715 local time, a focused swarm of earthquakes was interpreted as the start of a new ongoing eruption on the south flank (Tolbachinsky Dol) of Plosky Tolbachik volcano in east central Kamchatka, Russia (Figure 1a) [Samoylenko et al., 2012]. Visual observations on 29 November showed ash shooting from two fractures as well as long, rapidly moving lava flows. Although the initial ash clouds reached 6 kilometers in height, subsequent ashfall has been limited to the area around the main vents, and no permanent settlements are in danger from advancing lava flows (the closest settlements are about 40 kilometers from the volcano). Including this eruption, six different volcanoes are presently active in Kamchatka.

A catastrophic explosive eruption occurred 1700-1800 14C-years ago at Ksudach Volcano in Kamchatka. It was one of the AD greatest Plinian-type eruptions. It erupted 18-19 km3 of pyroclastic material and produced a collapse caldera 4 × 6.5 km in size and 6.5-7 km3 in volume. The eruptive column rose to a height of 23 km. It was the last caldera-forming eruption in the Kuril-Kamchatka region. It resembled an eruption that occurred at Krakatau in 1883 in type and size. The eruption was bound to have a climatic impact, impaired the Earth's ozone layer, and produced an acid peak in the Greenland ice sheet. -from Journal summary

The births (ages) of most of the active volcanoes, calderas, and large craters produced by caldera-resembling eruptions (subcaldera craters) were dated as a result of geological, geomorphological, tephrochronological, and isotopic studies. The dated active volcanoes were found to be fairly young formations, the age of the oldest being 40-50 thousand years. Most of the presently highly active volcanoes had been born at the very end of the late Pleistocene or during the Holocene. Carbon-14 ages were determined for the majority of the Holocene volcanoes. The periods of time when Holocene volcanoes had been synchronously active were 7500-7800 and 1300-1800 years ago. -from Journal summary

Remnants of five catastrophic lahars have been discovered, described, and dated by the carbon-14 method. They occurred during eruptions of Avacha (violent explosions with voluminous juvenile pyroclastics) and Koryakskiy (large fissure lava flows): 3500 to 3200 14C years ago or 1900-1500 years B.C. These lahars were much higher in vigor, hazard, and effect on the environment than the lahars generated by the historic eruptions of these volcanoes. -from Journal summary

Four Plinian eruptions of Ksudach have been reconstructed and dated by the carbon-14 method. The eruptions produced three collapse calderas: the KS1 eruption formed Caldera V 1700-1800 years ago, the KS2 and KS3 events produced Caldera IV 6000-6100 years ago, and the KS4 eruption formed Caldera III 8700-8800 years ago. The most violent eruption was the KS1 event. The sizes of the calderas were 4 × 6.5 km (V), 5 × 6 km (IV), and presumably 2-3 km across (III). Juvenile material was erupted in a rhythmic manner. The composition of the products was dominated by andesite (KS2 and KS4), dacite and rhyodacite (KS3), and rhyodacite (KS1). It is assumed that all caldera-forming eruptions were triggered by the injection of a new portion of high-temperature basic magma and its mixing with the cooling acid magma of the preexisting source. -from Journal summary

The chronology, dynamics, and parameters of seven large eruptions of Avacha Volcano were reconstructed for its IAv andesitic period 7250-370014C years B.P., which began after a >2000-year period of relative quiescence. Their juvenile (andesitic pyroclastics) and resurgent products are described, and the geological and geomorphological consequences are evaluated. The largest eruption occurred 715014C years B.P. (8-10 km3 of erupted material). The subsequent events occurred 5700 (≥0.34 km3), 5600 (≥0.4 km3), 5500 (>1.34 km3), 5000 (≥0.5 km3), 4500 (>1.1 km3), and 4000 (≥0.6 km3) 14C years B.P. The erupted rocks were dominated by tephra; pyroclastic flows occurred only during the events of 5500 and 5000 years ago. It is believed that most of the eruptions produced acid peaks of varying intensity in the Greenland ice sheet.